Fuel systems for internal combustion engines, and, in particular, diesel, gasoline and turbine engines have a high pressure fuel pump which is actuated in timed relationship to deliver fuel under pressure to the combustion spaces of the engine. Examples are new generations of electronically-controlled diesel engines which have unit injectors and gasoline engines with injectors located at either the throttle body or the individual cylinders. Air and fuel vapor can cause malfunctions or "vapor lock" in these systems and prevent proper metering of the fuel for injection and proper combustion. The emerging new diesel and gasoline/gasohol engines which utilize injectors operate with an excess of fuel that is returned to the fuel tank, tending to create pressure pulsations as the injectors open and close during normal operation. When a flowing liquid is suddenly stopped, interrupted or exposed to certain valving action, a pressure wave is created since the fluid is not sufficiently elastic to absorb the energy, pressure waves or pulsations created in the fluid. The pulsations travel back through the incoming column of fuel to the fuel pump and other components, such as sensors, where the pulsations may cause fatigue damage, decrease the efficiency of the fuel pump and harm valves, gaskets, fasteners, sensors and other fuel system components.
Many fuel system apparatuses and methods have been created in an attempt to reduce the magnitude of the pressure pulsations caused by the sudden closing of the valves or injectors and by the abrupt halting of moving fluid. One such known apparatus and method is to utilize a pressurized reservoir by which incoming fuel is pumped into the reservoir from the fuel pump. Once the reservoir is pressurized, the fuel is forced out of the reservoir wherein the fuel travels downstream to the fuel injectors of the engine. Such fuel reservoirs may allow for dampening of pulsations within the fuel as well as allowing for the purging of air and vapor that may exist within the fuel, but such fuel reservoirs are subject to excessive back flow or siphoning of the fuel such that fuel is allowed to drain back from the fuel injectors upon the fuel delivery system being shut down. When the fuel delivery system is shut down, the fuel pump stops delivering pressurized fuel to the reservoir, and atmospheric pressure is allowed to enter the system via the fuel tank thus creating a siphoning effect between the fuel reservoir and the fuel injectors of the engine. When the siphon occurs, the fuel from the fuel injectors may drain back to the fuel tank or back to the reservoir such that the fuel level in the fuel injectors of the engine may become so low that the fuel injectors do not have a sufficient amount of fuel to start the engine upon restarting the system. Thus, the fuel injectors may not have an ample amount of fuel to start the engine until the fuel pump reprimes and refills the entire fuel delivery system.
Other known designs have addressed this problem by mounting a fuel reservoir adjacent the fuel gallery of the engine so that the desired fuel level in the fuel gallery corresponds to a desired fuel level in the fuel reservoir. The desired fuel level maintains a sufficient amount of fuel within the fuel gallery when the fuel delivery system is shut down so that the engine will restart quickly and efficiently. Such a solution has a major drawback in that it is dependent on the fuel reservoir being mounted and maintained at a predetermined level corresponding to the fuel level within the fuel gallery of the engine. Thus, if the fuel reservoir is mounted too high or too low or at an angle with respect to the engine, the level of fuel within the fuel gallery and the fluid reservoir may be affected thus affecting the start-up performance of the engine. In addition, such known designs are placed within the incoming or supply side of the fuel line, and therefore, the return or exiting side of the fuel line does not prevent the drain-back of fuel caused by excessive back flow.
Thus, it would be desirable to provide an apparatus and method for reducing the magnitude of the pressure pulsations created by the sudden closing of valves and injectors and by the abrupt halting of moving fluid. It would also be desirable to provide an apparatus and method that would function to check excessive back flow and siphoning of fluids on both the supply and return sides of the fuel line so as to maintain a sufficient level of fuel within the fuel injectors during starting and stopping of the engine.